Removing diolefins from petroleum fractions by forming codimers with cyclic diolefins and distilling



June 26, 1956 w. D. SEYFRIED 2,752,406

REMOVING DIOLEFINS FROM PETROLEUM FRACTIONS BY FORMING CODIMERS WITH CYCLIC DIOLEF'INS AND DISTILLING Filed April 11, 1952 DiOLEFIN-FREE GASOLINE CYCLOPENTADIENE REACTION ZON5 GASOLINE l3 comm/mus J4 v ,\.\r i H \|a4111u 7] 350- 450! I I I9" 2;? I5 16 ISOPRENE 30 CYCILOPENTADIENE DEPOLYMERIZATION 201w:

HEA VIER IN VE NTOR.

Wilson D. Seyfr'r'ed,

States REMOVING DIOLEFIWS FRQM PETROLEUM FRACTIONS BY FORMING CODllVIERS WITH CYCLIC DIOLEFINS AND DISTILLING Application April 11, 1952, Serial No. 281,717

6 Claims. (Cl. 260-6815) The present invention is directed to a method for removing and recovering diolefins from hydrocarbon fractions. More particularly, the invention is directed to a method for producing a substantially diolefin-free gasoline fraction and recovering pure diolefins therefrom. In its more specific aspects, the invention is directed to a method for removing acyclic diolefins from a hydrocarbon fraction containing them.

The present invention may be briefly described as involving a method for removing acyclic diolefins from gasoline hydrocarbons and the like which are deficient in or do not contain conjugated cyclic diolefins. In my invention, there is added to such hydrocarbon fractions containing conjugated acyclic diolefins a sufficient amount of a conjugated cyclic diolefin having a five carbon atom ring to react with the acyclic conjugated diolefin to form a codimer of the acyclic and the cyclic conjugated diolefins. The acyclic diolefin-containing hydrocarbon fraction to which cyclic diolefin is added is reacted at a temperature in the range between 350 and 450 F. to form a codimer of said diolefins. Thereafter the product is distilled to recover the codimer and a hydrocarbon fraction substantially free of diolefins.

The hydrocarbon fraction or gasoline substantially free of diolefin is a desirable motor fuel since the diolefins and other reactive material which contribute to engine deposit forming tendencies on employment as a fuel in the motor have been removed by reaction with the conjugated cyclic diolefin added to the hydrocarbon or gasoline.

The codimer which is formed in accordance with the present invention may be employed as an insecticide; it may be halogenated to form chemical intermediates; or it may be subjected to a depolymerization operation to recover from the codimer the acyclic and cyclic diolefins as separate streams. Also by controlling the amount of cyclic diolefins added, it is possible to control the formation of a specific codimer which may be subjected to a simultaneous dehydrogenation-hydrogenation reaction to form desirable compounds such as methyl indanes.

The feed stock of the present invention will ordinarily be a hydrocarbon fraction such as a gasoline boiling in the range from about 80 F. to a maximum of about 320 F. Such fractions may contain acyclic diolefins such as isoprene, piperylenes and heXadiene-l,3 as well as other unsaturated compounds which contribute to the formation of deposits when the gasoline is employed as a motor fuel. In accordance with the present invention, 1 add to such gasolines a sufficient amount of cyclopentadiene and the like to react substantially completely with acyclic conjugated diolefins originally contained in such farction. I add an amount of cyclic conjugated diolefins sufficient to provide a ratio of cyclic diolefin to acyclic diolefin in the range from 0.1 :1 to 120.1.

The boiling range of the feed stock of the present invention is adjusted so that its final boiling point is no higher than the boiling range of the codimers formed by the reaction of cyclic and acyclic diolefins. For exatent "ice ample, if the feed stock contains isoprene, and the added cyclic diolefin is cyclopentadiene, the final boiling point of the feed stock chosen will be no higher than 320 F. so that the codimer which boils in the range from 320 to 350 F. may be separated as bottoms stream by fractionation.

It may be desirable to separate the feed stock into two fractions, one boiling below 320 F. and containing C5 acyclic diolefins, and a higher boiling C5-free fraction containing acyclic diolefins of 6 and 7 carbon atoms. The lighter fraction is then treated, according to my invention, with cyclopentadiene, and the heavier fraction with a substituted cyclopentadiene containing six or more carbon atoms.

The acyclic conjugated diolefin employed may be isoprene, tranpiperylene and the like as mentioned supra. The cyclic conjugated diolefin added to the acyclic conjugated diolefin feed may suitably be a 5 carbon atom ring compound illustrated by cyclopentadiene, S-methylcyclopentadienel ,3 and 2-methylpentadiene-1,3.

The codimers formed in accordance with the practice of the present invention may be either one or both of the two possible codimers of an acyclic and a cyclic diolefin. By varying the ratio of the cyclic diolefin to the acyclic diolefin, it is possible to direct the reaction to produce a particular codimer. For example, the reaction between isoprene and cyclopentadiene proceeds as shown in the following equations:

By adding a sufficient amount of cyclopentadiene to provide an amount of cyclopentadiene at least equal to the amount of the acyclic diolefin, it is possible to produce as a predominant product the codimer as shown in Equation I supra. At much lower ratios the codimer as illustrated in Equation II predominates.

The invention will be further illustrated by reference to the drawing in which the single figure is a flow diagram of a preferred mode.

Referring now to the drawing, numeral 11 designates a charge line through which a gasoline containing acyclic conjugated diolefins is introduced. The gasoline may be either a thermally or catalytically cracked product and may suitably boil in the range of about and up to but not exceeding 320 F. in the case where the diolefins are isoprene and cyclopentadiene. This gasoline is, without treatment in accordance with the present invention, unsuitable for use as a motor fuel because it has a tendency to deposit large amounts of resinous-like material in the internal combustion engine. Accordingly I add to the gasoline containing the acyclic diolefin flowing through line 11 a sufiicient amount of a conjugated cyclic diolefin to react with the acyclic conjugated diolefin. Thus I introduce through line 12 cyclopentadiene in an amount in the range given before to provide a suitable ratio for reaction as desired and the mixture of gasoline now containing acyclic and cyclic conjugated diolefins is introduced into a reaction zone 13 provided with a heating means illustrated by a coil 14 through which is flowed a heating fluid, such as superheated steam, introduced by line 15 and withdrawn by line 16. The temperature in reaction zone 14 is maintained at a temperature in the range between 350 and 450 F. to form the codimers indicated above. If a temperature below 350 F. were employed, the amount of the codimer produced would be relatively small while above 450 F. there is danger of decomposition of the codimers. The feed is allowed to remain in the reaction zone 13 a sufiicient length of time for substantially complete reaction of the cyclic and acyclic conjugated diolefins to form the codimers. This time will ordinarily be in the range from 10 minutes to 120 minutes and the reaction zone is of a sufiicient size and capacity to provide a sufiicient residence time to allow the reaction to go substantially to completion.

The reacted product containing either one or both of the codimers is withdrawn from reaction zone 13 by line 17 and introduced thereby into a fractional distillation zone 18 which is provided with heating means illustrated by a steam coil 19. The fractional distillation zone 18 may be a series of distillation towers but for purposes of simplifying this description is shown as a single distillation tower which is assumed to be provided with all auxiliary equipment usually associated with such distillation equipment including means for inducing reflux, cooling and/or condensing means and internal vaporliquid contacting means for insuring proper contact between vapor and liquid. Conditions are adjusted in distillation zone 18 to remove the substantially diolefin-free gasoline as an overhead fraction through line 20 and to withdraw by line 21 the polymerized product including the codimer. The codimers boil in the range from 320 to 350 F. The product may be withdrawn from the system by opening valve 22 in line 21 for use of the codimers as has been indicated or preferably the codimers are directed through line 23 controlled by valve 24 to a depolymerization zone 25 wherein the polymerized .diolefins are subjected to a temperature in the range between 600 to 1000 F. whereby the codimer is depolymerized to the monomers. The depolymerized product is then withdrawn from depolymerization zone 25 by line 26 and introduced thereby into a second fractional distillation zone 27 which may be similar in all respects to fractional distillation zone 18. Fractional distillation zone 27 is provided with a heating means illustrated by steam coil 28 for adjustment of temperature and pressure therein to allow withdrawal as overhead fraction by line 29 the isoprene originally contained in the gasoline introduced by line 11. The cyclopentadiene, originally introduced to line 11 by line 12, may be withdrawn and recovered by line 30 and may by recycled thereby to line 12 for reuse in the process. Heavier monomers and/or polymers may be discharged by line 21.

It will be seen from the foregoing description taken with the drawing that I have provided a readily adaptable process whereby the quality of the gasoline containing diolefins may be substantially improved. My invention is advantageous over the prior art where sulfuric acid treatment or treatment with a bed of clay has been employed in removing diolefins. Such processes suiter an economic disadvantage over my invention because of product loss and consumption of chemicals and other valuable materials. My invention is also advantageous over hydrogenation of diolefins since such facilities require large capital expenditures and also unless such operations are controlled impair to a marked extent the octane number of gasoline by hydrogenating not only the diolefins but also the mono-olefins which are beneficial in that they do not form resinous materials to a great extent and in that monoolefins have a beneficial efifect on the octane number.

The nature and objects of the present invention having been completely described and illustrated, what I wish to claim as new and useful and to secure by Letters Patent is:

1. A method for removing diolefins from a hydrocarbon fraction boiling in the range from about 80 to about 320 F. containing conjugated acyclic diolefins which comprises adding to said hydrocarbon fraction containing conjugated acyclic diolefins a conjugated cyclic diolefin having a five carbon atom ring in an amount sufiicient to provide a ratio of cyclic diolefin to acyclic diolefin in the range from 0.1:1 to 1:1 to react with the conjugated acyclic diolefins, heating the hydrocarbon fraction to which cyclic diolefin has been added to a temperature in the range between 350 and 450 F. for a time sufficient to react substantially completely said diolefins and to form a codimer of said diolefins and distilling the reacted hydrocarbon fraction to recover a substantially diolefinfree hydrocarbon fraction and said codimer.

2. A method for removing diolefins from a gasoline fraction boiling in the range from about to about 320 F. containing acyclic diolefins which comprises add ing to said gasoline fraction a sufficient amount of a conjugated cyclic diolefin having a five carbon atom ring to provide a ratio of cyclic diolefin to acyclic diolefin in the range from 0.1 :1 to 1:1 to react with said acyclic diolefin, reacting said gasoline containing acyclic and cyclic diolefins at a temperature in the range between 350 and 450 F. for a sufiicient length of time to form a codimer of said diolefins and distilling the reacted gasoline to recover a substantially diolefin-free gasoline and said codimer.

3. A method for removing diolefins from a hydrocarbon fraction containing acyclic diolefins and boiling in the range from about 80 to about 320 P. which comprises adding to said hydrocarbon fraction containing acyclic diolefins a sufficient amount of a conjugated cyclic diolefin having a five carbon atom ring to provide a ratio of cyclic diolefin to acyclic diolefin in the range from 0.1:1 to 1:1 to react with said acyclic diolefins, reacting said hydrocarbon containing acyclic and cyclic diolefins at a temperature in the range between 350 and 450 F. for a time from about 10 minutes to minutes to form a product containing a codimer of said diolefins and distilling said product to recover a substantially diolefin-free hydrocarbon fraction and said codimer.

4. A method for removing diolefins from a gasoline boiling in the range from about 80 to about 300 F. containing acyclic diolefins which comprises adding cyclopentadiene to said gasoline containing acyclic diolefins in an amount sufficient to provide a ratio of cyclopentadiene to acyclic diolefin in the range from 0.1:1 to 1:1 to react with said acyclic diolefins, reacting said gasoline-containing acyclic diolefins and cyclopentadiene at a temperature in the range from about 350 to about 450 F. for a time in the range between about 10 minutes and 120 minutes to form a product containing a substantial amount of a codimer of said cyclic diolefins and cyclopentadiene and distilling said reacted gasoline to recover a substantially diolefin-free gasoline and said codimer.

5. A method for removing diolefins from a gasoline containing isoprene and boiling in the range from about 80 to about 320 F. which comprises adding a sutficient amount of cyclopentadiene to said gasoline to provide a ratio of cyclopentadiene to isoprene in the range from 0.1:1 to 1:1 to react with said isoprene, reacting said gasoline-containing isoprene and cyclopentadiene at a temperature in the range between 350 and 450 F. for a sufiicient length of time to form a product containing a substantial amount of a codimer of said isoprene and cyclopentadiene and distilling said product to recover a substantially diolefin-free gasoline and said codimer.

6. A method in accordance with claim 5 in which the codimer is subjected to depolymerization conditions to form a second product containing isoprene and cyclopentadiene.

References Cited in the file of this patent UNITED STATES PATENTS Re. 22,671 Morris et a1 Aug. 28, 1945 2,355,392 Oberfell Aug. 8, 1944 2,401,414 Doumani et al. June 4, 1946 2,508,922 Luten et al May 23, 1950 

1. A METHOD FOR REMOVING DIOLEFINS FROM A HYDROCARBON FRACTION BOILING IN THE RANGE FROM ABOUT 80* TO ABOUT 320* F. CONTAINING CONJUGATED ACYCLIC DIOLEFINS WHICH COMPRISES ADDING TO SAID HYDROCARBON FRACTION CONTAINING CONJUGATED ACYCLIC DIOLEFINS A CONJUGATED CYCLIC DIOLEFIN HAVING A FIVE CARBON ATOM RING IN AM AMOUNT SUFFICIENT TO PROVIDE A RATIO OF CYCLIC DIOLEFIN TO ACYCLIC DIOLEFIN IN THE RANGE FROM 0.1:1 TO 1:1 TO REACT WITH THE CONJUGATED ACYCLIC DIOLEFINS, HEATING THE HYDROCARBON FRACTION TO WHICH CYCLIC DIOLEFIN HAS BEEN ADDED TO A TEMPERATURE IN THE RANGE BETWEEN 350* AND 450* F. FOR A TIME SUFFICIENT TO REACT SUBSTANTIALLY COMPLETELY SAID DIOLEFINS AND TO FORM A CODIMER OF SAID DIOLEFINS AND DISTILLING THE RACTED HYDROCARBON FRACTION TO RECOVER A SUBSTANTIALLY DIOLEFINFREE HYDROCARBON FRACTION AND SAID CODIMER. 